Breakpoints in symbols with ABI tags (PR c++/19436)

Trying to set a breakpoint in a function with an ABI tag does not work
currently.  E.g., debugging gdb itself, we see this with the
"string_printf" function:

 (top-gdb) b string_print                               [TAB]
 (top-gdb) b string_printf[abi:cxx11](char const*, ...) [RET]
 No source file named string_printf[abi.
 Make breakpoint pending on future shared library load? (y or [n])

Quoting doesn't help:
 (top-gdb) b 'string_printf[abi:cxx11]'(char const*, ...)
 malformed linespec error: unexpected string, "(char const*, ...)"
 (top-gdb) b 'string_printf[abi:cxx11](char const*, ...)'
 No source file named string_printf[abi.
 Make breakpoint pending on future shared library load? (y or [n]) n

This patch fixes this, and takes it a bit further.

The actual symbol name as demangled by libiberty's demangler is really

 string_printf[abi:cxx11](char const*, ...)

however, this patch makes it possible to set the breakpoint with

 string_printf(char const*, ...)

too.  I.e., ignoring the ABI tag.

And to match, it teaches the completer to complete the symbol name
without the ABI tag, i.e.,

  "string_pri<TAB>"  -> "string_printf(char const*, ...)"

If however, you really want to break on a symbol with the tag, then
you simply start writing the tag, and GDB will preserve it, like:

  "string_printf[a<TAB>"  -> "string_printf[abi:cxx11](char const*, ...)"

Grows the gdb.linespec/ tests like this:

  -# of expected passes           8977
  +# of expected passes           9176

gdb/ChangeLog:
2017-11-29  Pedro Alves  <palves@redhat.com>

	PR c++/19436
	* NEWS: Mention setting breakpoints on functions with C++ ABI
	tags.
	* completer.h (completion_match_for_lcd) <match,
	mark_ignored_range>: New methods.
	<finish>: Consider ignored ranges.
	<clear>: Clear ignored ranges.
	<m_ignored_ranges, m_finished_storage>: New fields.
	* cp-support.c (cp_search_name_hash): Ignore ABI tags.
	(cp_symbol_name_matches_1, cp_fq_symbol_name_matches): Pass the
	completion_match_for_lcd pointer to strncmp_iw_with_mode.
	(test_cp_symbol_name_cmp): Add [abi:...] tags unit tests.
	* language.c (default_symbol_name_matcher): Pass the
	completion_match_for_lcd pointer to strncmp_iw_with_mode.
	* linespec.c (linespec_lexer_lex_string): Don't tokenize ABI tags.
	* utils.c (skip_abi_tag): New function.
	(strncmp_iw_with_mode): Add completion_match_for_lcd parameter.
	Handle ABI tags.
	* utils.h (strncmp_iw_with_mode): Add completion_match_for_lcd
	parameter.

gdb/testsuite/ChangeLog:
2017-11-29  Pedro Alves  <palves@redhat.com>

	PR c++/19436
	* gdb.linespec/cpls-abi-tag.cc: New file.
	* gdb.linespec/cpls-abi-tag.exp: New file.

gdb/doc/ChangeLog:
2017-11-29  Pedro Alves  <palves@redhat.com>

	PR c++/19436
	* gdb.texinfo (Debugging C Plus Plus): Document setting
	breakpoints in functions with ABI tags.

1 files changed, 43 insertions, 0 deletions

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 7a71739..4f55222 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -15128,6 +15128,49 @@ the same notation that is used to declare such symbols in C@t{++}: type
 also use the @value{GDBN} command-line word completion facilities to list the
 available choices, or to finish the type list for you.
 @xref{Completion,, Command Completion}, for details on how to do this.
+
+@item @r{Breakpoints in functions with ABI tags}
+
+The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
+correspond to changes in the ABI of a type, function, or variable that
+would not otherwise be reflected in a mangled name.  See
+@url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
+for more detail.
+
+The ABI tags are visible in C@t{++} demangled names.  For example, a
+function that returns a std::string:
+
+@smallexample
+std::string function(int);
+@end smallexample
+
+@noindent
+when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
+tag, and @value{GDBN} displays the symbol like this:
+
+@smallexample
+function[abi:cxx11](int)
+@end smallexample
+
+You can set a breakpoint on such functions simply as if they had no
+tag.  For example:
+
+@smallexample
+(gdb) b function(int)
+Breakpoint 2 at 0x40060d: file main.cc, line 10.
+(gdb) info breakpoints
+Num     Type           Disp Enb Address    What
+1       breakpoint     keep y   0x0040060d in function[abi:cxx11](int)
+                                           at main.cc:10
+@end smallexample
+
+On the rare occasion you need to disambiguate between different ABI
+tags, you can do so by simply including the ABI tag in the function
+name, like:
+
+@smallexample
+(@value{GDBP}) b ambiguous[abi:other_tag](int)
+@end smallexample
 @end table
 
 @node Decimal Floating Point